Clutch assembly

Abstract

 This invention relates to a clutch assembly capable of selectively changing over power transmission routes, in which by effectively engaging and disengaging an engaging member located between a driving side and a driven side, transmission and nontransmission of power from the driving side to the driven side can be seriously selected.

Description

1. Field of the Invention

[0001] This invention relates to a clutch assembly capable of changing over transmission and nontransmission of the prime moving force selectively.

2. Description of the Prior Art

[0002] Conventionally, as a clutch assembly to selectively transmit a force of a driving source to a driven object, for example, an engaging clutch is known. For instance, the Japanese Unexamined Patent Publication No. 60-26821 dis­closes a clutch assembly capable of coupling a driving body to a driven body, by forming a plurality of engaging holes in the driven body, and retractably provided engaging shafts to be driven with the engaging holes in the driven body, with the driving body and driven body being arranged on a same center line. In this clutch assembly, when trans­ferring from the state of transmitting the driving force with the driving shafts and driven shafts being coupled together to the state of nontransmission, it is necessary to draw back the engaging shafts which are engaged with the engaging holes to be separated from the driving body. At this time, on the contact surface between the engaging holes and engaging shafts, there is a surface pressure P generat­ed, corresponding to the shaft torque being transmitted (that is, the rotary load of the driven body). Supposing the coefficient of friction on the contact surface to be µ, a force P x µ is required to isolate the engaging shafts from the engaging holes. Therefore, a considerably large force is needed to separate while transmitting a large shaft torque. Accordingly, when the engaging shafts are moved forward and backward by a solenoid or the like, a very large solenoid is required. In addition, the reliability of action is inferior.

SUMMARY OF THE INVENTION

[0003] It is hence a primary object of this invention to pre­sent a clutch assembly capable of obtaining a secure change­over action in a simple structure.

[0004] To achieve this object, a clutch assembly according to this invention comprises: a driving member; an engaging member movable between a first position where said engaging member engages said driving member and a second position where said engaging member is apart from said driving member; a first thrusting means for thrusting said engaging member toward said first position; a driven member mounting thereon said engaging member and said first thrusting means and driven by said driving member through said engaging member when said engaging member is in said first position; a releasing member movable between a position where said releasing member abuts against said engaging member and a position where said releasing member is apart from said engaging member; and a second thrusting means for thrusting said engaging member through said releasing member toward said second position, wherein said engaging member is moved by a driving force of said driving member to disengage from said driving member when said releasing member abuts against said engaging member, and further moved by the thrusting force of said second thrusting means through said releasing member to said second position after having disengaged from said driving member whereby said driven member is released from said driving member.

[0005] This invention, in an extremely simple structure as described above, can securely select transmission and nontransmission of the driving force from the driving member to the driven member, by means of the engag­ing member located between the driving member and driven member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] 

FIG. 1 is a sectional view of essential part of a clutch assembly according to a first embodiment of this invention, FIG. 2 to FIG. 6 are plans of the same embodi­ment;

FIG. 7 to FIG. 9 are plans of a second embodiment of this invention;

FIG. 10 and FIG. 12 to FIG. 14 are plans of a clutch assembly in a third embodiment of this invention, and FIG. 11 is a sectional view of essential parts of the same embod­iment;

FIG. 15 and FIG. 17 to FIG. 20 are plans of a clutch assembly in a fourth embodiment of this invention, and FIG. 16 is a sectional view of essential parts of the same embod­iment;

FIG. 21, and FIG. 23 to FIG. 26 are plans of a clutch assembly in a fifth embodiment of this invention, and FIG. 22 is a sectional view of essential parts of the same embod­iment; and

FIG. 27, and FIG. 29 to FIG. 32 are plans of a clutch assembly in a sixth embodiment of this invention, and FIG. 28 is a sectional view of essential parts of the same embod­iment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The clutch assembly in a first embodiment of this in­vention is now described below while referring to the accom­panying drawings.

[0008] In FIG. 1, driving gear 12 which is always rotated and driven by a motor (not shown) is rotatably supported on a shaft 11 planted on a chassis 10, and a projection 13 is disposed at a specified interval on its inner circumference. A driven gear 19 which possesses a boss 17 to slidably guide a clutch member 15 and a groove 18 to be fitted with the clutch member 15, being engaged with a guide groove 16 dis­posed on the clutch member 15 having a first projection 14 keeping an engaging relation with a projection 13 is rota­tably supported on the shaft 11. The clutch member 15 is thrusted in the rightward direction in FIG. 1 by means of a spring 20 stretched over the driven gear 19, and it is en­gaged with the projection 13 provided on the driving gear 12. Therefore, the torque of the driving gear 12 is trans­mitted to the driven gear 19 by way of the clutch member 15. If, at this time, the clutch member 15 moves in the leftward direction, resisting the thrusting force of the spring 20, the engagement of the first projection 14 and projection 13 is released, and the torque of the driving gear 12 is not transmitted to the driven gear 19. Incidentally, the clutch member 15 also possesses a second projection 21 which abuts against an abutting member described below. A supporting plate 22 is designed to move reciprocally on the chassis 10 between the non-acting position shown in FIG. 2 and acting position shown in FIG. 3, by a known means (for example, driving of plunger by solenoid), and also to stop at the acting position shown in FIG. 3. Shafts 23, 24 are planted on the supporting plate 22 so as to support an abutting member 25 slidably in the lateral direction in FIG. 1, being engaged with a guide groove 26 of the abutting member 25. Meanwhile, the abutting member 25 receives a thrusting force in the leftward direction in FIG. 1 by a compression spring 27 placed between it and the supporting plate 22, but it is stopped at the position shown in FIG. 1 as the shaft 24 abuts against the edge of guide groove 26. Here, when the abutting member 25 is moved in the rightward direction in FIG. 1, resisting the thrusting force of the compression spring 27, a stopping surface 28 abuts against the shaft 23, and it is designed to be stopped at the position shown in FIG. 4. That is, a first abutting portion 29 and a second abutting portion 30 provided at the edge of the abutting member 25 abut against a second projection 21 of the clutch member 15, and the abutting member 25 moves from the posi­tion in FIG. 2 rightward to the position shown in FIG. 4, where it is stopped.

[0009] The operation is described hereinafter.

[0010] In FIG. 2, the supporting plate 22 is stopped at the non-acting position, and the second projection 21 of clutch member 15 and the abutting member 15 are in a relation not to abut against each other. Therefore, the clutch member 15 is thrusted in the upper obliquely rightward direction in FIG. 2, and the first projection 14 and the projection 13 on the driving gear 12 are engaged with each other. For exam­ple, when the driving gear 12 is rotated and drive in the clockwise direction by a motor (not shown) in FIG. 2, the clutch member 15 having the first projection 14 engaged with the projection 13 is also rotated and driven in the clock­wise direction. Therefore, the motor torque is also trans­mitted to the driven gear 19, which rotates in the clockwise direction.

[0011] Next is explained the operation of not transmitting the torque of driving gear 12 to the driven gear 19. The sup­porting plate 22 is removed from the non-acting position shown in FIG. 2 to the acting position shown in FIG. 3 by, for example, a solenoid (not shown), and is stopped at the acting position. At this time, the load on the solenoid needs only a small force because it is enough to move the supporting plate 22 mounted on the abutting member 25. As a result, the first abutting portion 29 disposed at the edge of the abutting member 25 on the supporting plate 22 and the second projection 21 of the clutch member 15 are ready to abut against each other. When the driving gear 12 is fur­ther rotated clockwise from the state shown in FIG. 3, the second projection abuts against the first abutting portion 29. At this time, a load torque T is applied to the driven gear 19. Therefore, supposing the distance from the center of shaft 11 to the contact point of the projection 13 of driving gear 12 and the first projection 14 of clutch member 15 to be R and the tangential force at contact point to be N, the following relation is established:
N = T/R ---- (1)

[0012] And supporting the coefficient of friction at the con­tact point to be µ, and the frictional force between clutch member 15 and groove 18 to be fʹ, the frictional force f in the sliding direction on the driven gear 19 of clutch member 15 is
f = µ x N + fʹ = µ x T/R + fʹ ---- (2)

[0013] Therefore, in the state shown in FIG. 4, the releasing force F to move the clutch member 15 in the direction to be separated from the driving gear 12 is required as defined below, supposing the thrusting force in the engaging direc­tion of clutch member 15 by the spring 20 to be P.
F = f + P ---- (3)

[0014] Incidentally, since the thrusting force of the com­pression spring 27 to thrust the abutting member 25 in the leftward direction in FIG. 7 is set smaller than said re­leasing force F, if the second projection 21 abuts against the first abutting portion 29, the engagement between the clutch member 15 and driving gear 12 is not disconnected, and the abutting member 25 is rotated in the rightward di­rection, resisting the thrusting force of the compression spring 27. As the driving gear 12 further rotates clock­wise, it becomes the state as shown in FIG. 4, and the move­ment of the abutting member 25 in the rightward direction is stopped as the shaft 23 and stopping surface 28 abut against each other. The driving gear 12 still continues to rotate until the second projection of the clutch member 15 abuts against the second abutting portion 30. At this time, since the rightward movement of the abutting member 25 is defined by the shaft 23 and stopping surface 28, the clutch member 15 moves in the leftward direction in FIG. 4 along the obli­que surface of the second abutting portion 30 of the abut­ting member 25 until reaching the position shown in FIG. 5, where the engagement of the first projection 14 of the clutch member 15 and the projection 13 of the driving gear 12 is disconnected, and the torque of the driving gear 12 is not transmitted to the driven gear 19. At this time, the frictional force f between the projection 13 and the first projection 14, and the frictional force fʹ between the clutch member 15 and groove 18 are eliminated, and only the thrusting force by the spring 20 acts on the clutch member 15, but since the thrusting force of the spring 20 is set smaller than that of the compression spring 27, the abutting member moves the clutch member 15 in the leftward direction, resisting the thrusting force of the spring 20, as shown in FIG. 6, and the projection 13 of the driving gear 12 and the first projection 14 of the clutch member 15 are completely separated from each other. Therefore, if vibration or other force is applied from outside, the clutch member 15 and the driving gear 12 are not engaged unexpectedly, and a secure releasing operation is effected.

[0015] Next, when the supporting plate 22 is moved from the nontransmitting state of torque shown in FIG. 6 to the posi­tion shown in FIG. 2 by means of solenoid (not shown), the clutch member 15 moves in the rightward direction in FIG. 6 by the thrusting force of the spring 20 along with the move­ment of the abutting member 25 until the first projection 14 and the projection 13 are engaged with each other, so that the torque of the driving gear 12 is transmitted to the driven gear 19 by way of the clutch member 15.

[0016] As mentioned above, when selecting transmission and nontransmission of the torque of the driving gear 12 to the driven gear 19, since the required force of the solenoid (not shown) to drive the supporting plate 2 is small, the solenoid may be reduced in size and saved in power consump­tion. At the same time, the reliability of operation is enhanced.

[0017] Meanwhile, in the above description, the rotation of the driving gear 12 is clockwise, but, needless to say, exactly the same operation and effect are obtained when rotated counterclockwise.

[0018] Or, the projection 13 is disposed at the inside of the driving gear 12, but it is not limited to the shown shape, and it is the same if a gear is formed or pin is planted.

[0019] A second embodiment of this invention is hereby de­scribed.

[0020] What is different from the constitution of the first embodiment is that a first abutting portion 29 and a second abutting portion 30 are disposed in order to move the abut­ting member 25 in the rightward direction from the position shown in FIG. 7, at the edge of the abutting member 25, by abutting against the second projection 21 of the clutch member 15. In addition, the abutting member 25 is provided with a dent 29a which is engaged with the second projection 21 of the clutch member 15 to define its rotation after the engagement of the clutch member 15 and driving gear 12 is released.

[0021] The operation of the second embodiment is as follows.

[0022] First the action of not transmitting the torque of the driving gear 12 to the driven gear 19 is explained. The supporting plate 22 is moved from the non-acting position to the acting position shown in FIG. 7 by means of a known means (such as solenoid), and it is stopped at this acting position. As a result, the first abutting portion 29 and second abutting portion 30 disposed at the edge of abutting member 25 on the supporting plate 22 and the second projec­tion 21 of the clutch member 15 are ready to abut against each other. Since the thrusting force of the compression spring 27 to thrust the abutting member 25 in the leftward direction in FIG. 7 is set smaller than the releasing force F for separating the engagement of the clutch member 15 and driving gear 12, if the second projection 21 abuts against the first abutting portion 29, the engagement of the clutch member 15 and driving gear 12 is not disconnected, and the abutting member 25 is moved in the rightward direction, resisting the thrusting force of the compression spring 27. The shape from the first abutting portion 29 to the dent 29a of the abutting member 25 is designed in a relation so that the stopping surface 28 may not be stopped by the shaft 23 if the abutting member 25 is moved in the rightward direc­tion due to abutting of the clutch member 15 against the second projection 21. The driving gear 12 continues to rotate clockwise, and the second projection 21 of the clutch member 15 abuts against the second abutting portion 30. In consequence, the abutting member 25 further moves in the rightward direction, but since the rightward movement of the abutting member 25 is defined by the shaft 23 and stopping surface 28, the clutch member 15 moves in the leftward di­rection in FIG. 7 along the oblique surface of the second abutting portion 30 of the abutting member 25 until reaching the position shown in FIG. 8, where the engagement of the first projection 14 of clutch member 15 and the projection 13 of driving gear 12 is disconnected, so that the torque of the driving gear 12 is not transmitted to the driven gear 19. At this time, the frictional force f between the pro­jection 13 and first projection 14 is eliminated, and only the thrusting force by spring 20 acts on the clutch member 15, but since the thrusting force of spring 20 is set small­er than that of compression spring 27, the abutting member 25 overcomes the thrusting force of spring 20 as shown in FIG. 9 to move the clutch member 15 in the leftward direc­tion, and the projection 13 of the driving gear 12 and the first projection 14 of the clutch member 15 are completely separated from each other. At this time, the second pro­jection 14 of the clutch member 15 is engaged with the dent 29a of the abutting member 25, thereby defining the rotation in both clockwise direction and counterclockwise direction of the driven gear 19. Therefore, if vibration or other force is applied from outside, the clutch member 15 and driving gear 12 are not unexpectedly engaged with each other, nor the driven gear 19 be rotated, so that secure engaging and disengaging operation is guaranteed.

[0023] Incidentally, as the means of defining the rotation of the driven gear 19 after the driving gear 12 of and clutch member 15 are disengaged, the dent 29a is provided in the abutting member 25, but its position and shape are not limited as shown in the drawing.

[0024] A third embodiment of this invention is described below while referring to FIG. 10 to FIG. 14.

[0025] What is different from the first embodiment is that, as shown in FIG. 10, the driven gear 19 possessing a boss 17 to slidably and rotatably guide the clutch member 15 by engag­ing with a guide groove 16 provided in the clutch 15 having a first projection 14 which is in an engaging relation with a projection 13, and a groove 18 having edge surfaces 18a, 18b for defining the amount of rotation in the clockwise direction and counterclockwise direction in FIG. 10 of the clutch member 15 is rotatably supported on a shaft 11. Furthermore, by the spring 20 stretched on the driven gear 19, the clutch member 15 is thrusted in the rightward direc­tion in FIG. 11, and is engaged with the projection 13 dis­posed on the driving gear 12. Therefore, the torque of the driving gear 12 is transmitted to the driven gear 19 by way of the clutch member 15 and edge surface 18a of the groove 18. The operation of this third embodiment is illustrated hereinafter.

[0026] If the driving gear 12 is rotated and driven in the clockwise direction by a motor (not shown) in FIG. 10, the clutch member 15 having the first projection 14 engaged with the projection 13 is rotated and driven in the clockwise direction. Therefore, the clutch member 15 is stopped by the edge surface 18a, and the motor torque is also transmit­ted to the driven gear 19, which is then put into clockwise revolution.

[0027] In the next step, when the supporting plate 22 is moved from the torque nontransmitting state shown in FIG. 12 to the position shown in FIG. 10 by a known means (such as solenoid), the clutch member 15 is moved in the rightward direction in FIG. 6 by the thrusting force of the spring 20 along with the movement of the abutting member 25 until the first projection 14 and the projection 13 are engaged with each other, so that the torque of the driving gear 12 is transmitted to the driven gear 15 through the clutch member 15. At this time, the clutch member 15 has a degree of freedom in the rotating direction, and, as shown in FIG. 13, if the first projection 13 abuts against the front ends of the projection 13, the clutch member 15 escapes by turning in the rotating direction of the driving gear 12, and is securely engaged with the adjacent projection as shown in FIG. 14. Therefore, only a very slight portion of the front end is engaged depending on the timing, and there is no problem for strength.

[0028] In this explanation, the rotation of driving gear 12 is clockwise, but if rotated counterclockwise, only the clutch member 15 is stopped by groove 18b, and all other operations and effects are exactly the same.

[0029] A fourth embodiment of this invention is described below in conjunction with FIG. 15 to FIG. 20.

[0030] In the drawings, a driving gear 12 which is always rotated and driven by a motor (not shown) is rotatably sup­ported on a shaft 11 planted on a chassis 10, and a projec­tion 13 is formed at a specified interval in this inside. A driven gear 19 possessing a boss 17 to slidably guide a clutch member 15 by engaging with a guide groove 16 provided in the clutch member 15 having a first projection 14 which is in an engaging relation with a projection 13, and a groove 18 which is fitted with the clutch member 15 is ro­tatably supported on the shaft 11. Furthermore, by the spring 20 stretch over the driven gear 19, the clutch member 15 is thrusted in the rightward direction in FIG. 16, and it is engaged with the projection 13 disposed on the driving gear 12. Therefore, the torque of the driving gear 12 is transmitted to the driven gear 19 through the clutch member 15. Here, if the clutch member 15 moves in the leftward direction in FIG. 16, overcoming the thrusting force of the spring 20, the engagement of the first projection 14 and the projection 13 is released, and it is so designed that the torque of the driving gear 12 may not be transmitted to the driven gear 19. Incidentally, the clutch member 15 also possesses a second projection 21 which abuts against an abutting member 25 mentioned below. On the outside of the driven gear 19 is provided a cam surface 32 at both side in the vicinity of the second projection 21 of the clutch mem­ber 15, and as abutting against the abutting member 25, the abutting member 25 is once moved in the rightward direction in FIG. 17 until the abutting relation between the cam sur­face 32 and abutting member 25 is disengaged, and the abut­ting member 25 is shaped so as to be able to press down the second projection 21 of the clutch member 15. The support­ing plate 22 moves reciprocally between the non-acting posi­tion shown in FIG. 15 and the acting position shown in FIG. 17 to FIG. 20, on the chassis 10, by a known means (for example, driving of plunger by solenoid), and is designed to be stopped at the position shown in FIG. 15 and FIG. 17. The supporting plate 22 has shafts 23, 24 planted thereon, which support the abutting member 25 slidably in the lateral direction in FIG. 15 as being engaged with the guide groove 26 in the abutting member 25. Meanwhile, the abutting mem­ber 25 receives a thrusting force in the leftward direction in FIG. 15 by the compression spring 27 loaded between it and the supporting plate 22, but since the shaft 26 abuts against the edge of the guide groove 26, the abutting member 25 is stopped at the position shown in FIG. 15.

[0031] The operation of this embodiment is as follows.

[0032] In FIG. 15, the supporting plate 22 is stopped at a non-acting position, in which the second projection 21 of clutch member 15 and abutting member 25 are in a non-abut­ting relation. Therefore, the clutch member 15 is thrusted in the obliquely right upward direction in FIG. 15 by the spring 20, and the first projection 14 and the projection 13 disposed on the driving gear 12 are engaged with each other. For example, if the driving gear 12 is rotated and driven in the clockwise direction in FIG. 15 by a motor (not shown), the clutch member 15 having the first projection 14 which is engaged with the projection 13 is also rotated and driven in the clockwise direction. Therefore, the motor torque is also transmitted to the driven gear 19, which also rates in the clockwise direction.

[0033] The direction of not transmitting the torque of driving gear 12 to driven gear 19 is described below. The support­ing plate 22 is moved by a known means (such as solenoid) from the non-acting position shown in FIG. 15 to the acting position shown in FIG. 17, and is stopped at this acting position. As a result, the abutting member 25 on the sup­porting plate 22 and the cam surface 32 are ready to abut against each other. When the driving gear 12 is rotated clockwise in the state shown in FIG. 17, the cam surface 32 and abutting member 25 abut against each other, and the abutting member 25 once moves in the rightward direction, overcoming the thrusting force of the compression spring 27, /as is shown in FIG. 18. As the driving gear 12 moves further clockwise, it comes to the recess in the cam surface 32, and the second projection 21 abuts against abutting member 25. At this time, a load torque T is applied on the driven gear 19. Therefore, supposing the distance from the center of shaft 11 to the contact point of the projection 13 of driv­ing gear 12 and the first projection 14 of clutch member 15 to be R and the tangential force at contact point to be N, it follows that:
N = T/R ----- (4)

[0034] Furthermore, assuming the coefficient of friction at the contact point to be µ, and the frictional force acting between the clutch member 15 and groove 18 to be fʹ, the frictional force f in the sliding direction on the driven gear 19 of the clutch member 15 is expressed as follows:
f = µ x N + fʹ = µ x T/R + fʹ ----- (5)

[0035] Hence, the releasing force F to move the clutch member 15 in the direction to be separated from the driving gear 12 in the state shown in FIG. 18 is, assuming the thrusting force in the engaging direction of the clutch member 15 by the spring 20 to be P, required as defined below:
F = f + P ----- (6)

[0036] Incidentally, since the thrusting force of the com­pression spring 27 to thrust the abutting member 25 in the leftward direction in FIG. 18 is set larger than said re­leasing force F, when the second projection 21 abuts against the abutting member 25, the clutch member 15 moves in the leftward direction in FIG. 18, and the engagement of the clutch member 15 and driving gear 12 is disconnected. That is, when the driving gear 12 further rotates clockwise from the position shown in FIG. 18, the second projection 21 of the clutch member 15 abuts against the abutting member 25, and, as mentioned above, since the thrusting force of the compression spring 27 is set sufficiently larger than the force F, the abutting member 25 causes the clutch member 15 to move in the leftward direction until reaching the posi­tion shown in FIG. 19, where the engagement of the first projection of clutch member 15 and the projection 13 of driving gear 12 is disconnected, so that the torque of the driving gear 12 is not transmitted to the driven gear 19. Furthermore, the clutch member 15 is moved in the leftward direction up to the position shown in FIG. 20, and the pro­jection 13 of driving gear 12 and the first projection 14 of clutch member 15 are completely isolated from each other. Here, the thrusting force of the compression spring 27 acts on the driven gear 19 only while transferring to the non­transmitting state as the driven gear 19 and the abutting member 25 abut against each other, and in the stationary state of transmission of rotation, no effect is exerted on the rotation of driving gear 12 and driven gear 19. On the other hand, the front edge of the abutting member 25 is fitted with the gap in two cam surfaces 32 so as to define the rotation of the driven gear 19 in both clockwise and counterclockwise direction. Therefore, if vibration or other force is applied from outside, the clutch member 15 and driving gear 12 will not be unexpectedly engaged with each other, nor the driven gear 19 be put in revolution, so that a secure engaging and disengaging operation may be guaranteed.

[0037] According to this embodiment, as stated above, it is possible to change over securely to the nontransmitting state whether the transmission torque from the driving gear 12 to the driven gear 19 is small or large.

[0038] Next, from the state of not transmitting the torque shown in FIG. 20, when the supporting plate 22 is moved up to the position shown in FIG. 15 by a known means (for exam­ple, a solenoid), the clutch member 15 moves in the right­ward direction in FIG. 20 by the thrusting force of the spring 20 along with the movement of the abutting member 25 until the first projection 14 and projection 13 are engaged with each other, so that the torque of the driving gear 12 is transmitted to the driven gear 19 by way of the clutch member 15.

[0039] Incidentally, in this explanation, the rotation of the driving gear 12 is clockwise, but this embodiment is so constituted that similar operation and effect be obtained if rotated counterclockwise.

[0040] Or, the cam surface 32 is provided as the abutting portion for moving the abutting member 25 once in the rightward direction before the clutch member 15 abuts against the abutting member 25, but its shape is not limited to the one shown in the drawing, and a pin or the like may be planted instead.

[0041] Also, the projection 13 disposed on the inside wall of the driving gear 12 is not limited to the shape shown in the drawing, but a gear may be formed, or a pin may be planted instead.

[0042] Hereinafter is described a fifth embodiment of this invention while referring to FIG. 21 to FIG. 26.

[0043] In FIG. 21, a driving gear 12 which is always rotated and driven by a motor (not shown) is rotatably supported on a shaft 11 planted on a chassis 10, and a projection 13 is disposed at a specified interval on its inner circumference. The shaft also rotatably support a boss 17 which slidably guides a clutch member 15 by engaging with a guide groove 16 provided in the clutch member 15 possessing a first projec­tion 14 in an engaging relation with the projection 13, and a driven gear 19 which possesses a groove 18 to be fitted with the clutch member 15. By a spring 20 stretched above the driven gear 19, the clutch member 15 is thrusted in the rightward direction in FIG. 22, and is engaged with the projection 13 provided on the driving gear 12. Therefore, the torque of the driving gear 12 is transmitted to the driven gear 19 by way of the clutch member 15. If this clutch member 15 moves in the leftward direction in FIG. 22, resisting the thrusting force of the spring 20, the engage­ment of the first projection 14 and the projection 13 is released, and it is designed so that the torque of the driv­ing gear 12 is not transmitted to the driven gear 19. The clutch member also possesses a second projection 21 which abuts against an abutting member 25. On the outer circum­ference of the driven gear 19, there is a cam surface 32 which possesses a recess 32 which is narrower in width to­ward the thrusting direction of the clutch member, at both sides in the vicinity of the second projection 21 of the clutch member 15, and as it abuts against the abutting mem­ber 25, the abutting member 25 is moved once in the right­ward direction in FIG. 23, and the abutting relation of the cam surface 32 and abutting member 25 is cleared, so that the abutting member 25 may press down the second projection 21 of the clutch member 15. A supporting plate 22 moves reciprocally between the non-acting position shown in FIG. 21 and the acting position shown in FIG. 23, on the chassis 10 by means of a known means (for example, driving of plung­er by solenoid), and is designed to be stopped at the acting position shown in FIG. 21 and FIG. 23. Shafts 23, 24 are planted on the supporting plate 22, and they slidably sup­port the abutting member 25 in the lateral direction in FIG. 21 by engaging with a guide groove 26 in the abutting member 25. Incidentally, the abutting member 25 receives a thrust­ing force in the leftward direction in FIG. 21 by a compres­sion spring 27 located between it and the supporting plate 22, but since the guide 24 abuts against the edge of the guide groove 26, the abutting member 25 is stopped at the position shown in FIG. 21. Here, when the abutting member 25 is moved in the rightward direction in FIG. 23, overcom­ing the thrusting force of the compression spring 27, a stopping surface 28 abuts against the shaft 23, so that it may be stopped at the position shown in FIG. 25. Further­more, at the edge of the abutting member 25, there are a first abutting portion 34 which has a wider width toward the thrusting direction of the abutting member 25 and a second abutting portion 25 which can abut against the second pro­jection 21, so as to move the abutting member 25 in the rightward direction in FIG. 23 while abutting against the cam surface 32.

[0044] Its operation is as follows.

[0045] In FIG. 21, the supporting plate 22 is stopped at the non-acting position, in which the cam surface 32 and the first abutting portion 34 are in a non-abutting relation. Therefore, the clutch member 15 is thrusted in the obliquely right upward direction in FIG. 21 by the spring 20, and the first projection 14 and the projection 13 disposed on the driving gear 12 and are engaged with each other. For example, if the driving gear 12 is rotated and driven in the clock­wise direction by a motor (not shown) in FIG. 21, the clutch member 15 having the first projection 14 which is engaged with the projection 13 is also rotated and driven in the clockwise direction. Therefore, the motor torque is also transmitted to the driven gear 19, so that the driven gear 19 is rotated in the clockwise direction.

[0046] The operation of not transmitting the torque of the driving gear 12 to the driven gear 19 is described below. The supporting plate 22 is moved from the non-acting posi­tion shown in FIG. 21 to the acting position shown in FIG. 23 by a known means (such as solenoid), and is stopped at this acting position. As a result, the first abutting por­tion 34 of the abutting member 25 on the supporting plate 22 and the cam surface 32 of the driven gear 19 are ready to abut against each other. When the driving gear 12 is rotat­ed clockwise from the state shown in FIG. 23, the cam sur­face 32 and the first abutting portion 34 abut against each other, and the abutting member 25 is once moved in the rightward direction, resisting the thrusting force of the compression spring 27. Furthermore, when the driving gear 12 rotates clockwise, the first abutting portion 34 comes to the recess 33 as shown in FIG. 24, so that the second abut­ting portion 35 and the second projection 21 are ready to abut against each other. At this time, a load torque T is acting on the driven gear 19. Therefore, supposing the distance from the centre of the shaft 11 to the contact point of the projection 13 of driving gear 12 and the first projection 14 of clutch member 15 to be R and the tangential force at the contact point to be N, the following relation is established.
N = T/R ----- (7)

[0047] Moreover, assuming the coefficient of friction at the contact point to be µ, and the frictional force acting between the clutch member 15 and groove 18 to be fʹ, the frictional force f of the clutch member 15 in the sliding direction on the driven gear 19 is expressed as follows:
f = µ x N + fʹ = µ x T/R + fʹ ----- (8)

[0048] Therefore, in the state shown in FIG. 24, the releasing force F required to move the clutch member 15 in the direc­tion to be disengaged from the driving gear 12 is, assuming the thrusting force in the engaging direction of the clutch member 15 by the spring 20 to be P, required by the product:
F = f + P ----- (9)

[0049] At this time, since the thrusting force of the compres­sion spring 27 thrusting the abutting member 25 in the left­ward direction in FIG. 24 is set smaller than said releasing force F and is larger than the thrusting force P of the spring 20, when the second projection 21 abuts against the second abutting portion 35, the abutting member 25 moves in the rightward direction in FIG. 24, but its movement is defined by the shaft 23 and stopping surface 28. Therefore, when the driving gear 12 further rotates in the clockwise direction in FIG. 24, the clutch member 15 moves in the leftward direction toward the slope of the second abutting portion 35, and the engagement between the projection 13 and the first projection 14 is disconnected as shown in FIG. 25, and the torque of the driving gear 12 is not transmitted to the driven gear 19. After the disengagement between the projection 13 and the first projection 14, the clutch member 15 is further moved in the leftward direction up to the position shown in FIG. 26 by the thrusting force of the compression spring 27, resisting the thrusting force of the spring 20, until the projection 13 of the driving gear 12 is completely isolated from the first projection 14 of the clutch member 15.

[0050] Or if the load T fluctuates and becomes, for example, smaller than the set value, the clutch member 15 may be moved in the releasing direction only by the thrusting force of the compression spring 27, and if the load T increases, since the rightward movement of the abutting member 25 is defined by the shaft 23 and the stopping surface 28, the clutch member 15 can be securely moved in the releasing direction. Thus, if the load T fluctuates, a highly reli­able operation is guaranteed.

[0051] Here, the thrusting force of the compression spring 27 acts on the driven gear 19 only while transferring to the nontransmitting state as the driven gear 19 abuts against the abutting member 19, and in the stationary state of transmitting rotation, it exerts no effect on the rotation of the driving gear 12 or driven gear 19.

[0052] On the other hand, the first abutting portion 34 of the abutting member 25 is fitted to the recess 33 in the two cam surfaces 32 in order to define the rotation of the driven gear 19 in the clockwise and counterclockwise direction. Therefore, if vibration or other force is applied from out­side, the clutch member 15 and driving gear 12 will not be engaged unexpected with each other, nor the driven gear 19 be rotated largely, so that a secure disengaging operation may be effected.

[0053] In addition, since the recess 33 and the first abutting portion 34 are shaped as shown in the drawing, the first abutting portion 34 instantly drops into the recess 33, so that a sharp disengaging operation may be obtained.

[0054] As stated above, since the first abutting portion 34 to abut against the cam surface 32 and the second abutting portion 35 to press down the second projection 21 are pro­vided, the shape suited to an action may be freely set, and measures against abrasion can be effected individually, so that a clutch assembly of higher reliability may be ob­tained.

[0055] Next, when the supporting plate 22 is moved from the torque nontransmitting state shown in FIG. 26 up to the position shown in FIG. 21 by a known means (such as sole­noid), the clutch member 15 moves in the rightward direction in FIG. 26 by the thrusting force of the spring 20 along with the movement of the abutting member 25 until the first projection 14 is engaged with the projection 13, so that the torque of the driving gear 12 is transmitted to the driven gear 19 through the clutch member 15.

[0056] In this explanation, meanwhile, the rotation of the driving gear 12 is clockwise, but it is so constituted as to obtain the same operation and effect if rotated in the coun­terclockwise.

[0057] Incidentally, the cam surface 32 is provided as an abutting portion for moving the abutting member 25 once in the rightward direction before the clutch member 15 and the abutting member 25 abut against each other, but its shape is not limited to the one shown in the drawing, and pin or the like may be planted instead.

[0058] Besides, the projection 13 provided inside the driving gear 12 may not be limited to the shape shown in the draw­ing, and a gear may be formed or a pin may be planted, in­stead.

[0059] A sixth embodiment of this invention is now described in relation to FIG. 27 to FIG. 32.

[0060] In the drawing, a driving gear 12 which is always ro­tated and driven by a motor (not shown) is rotatably sup­ported on a shaft 11 planted on a chassis 10, and a projec­tion 13 is provided in its inside at a specified interval. Engaging members 36, 37 possessing projections 36a, 37a which can be individually engaged with the projection 13 are slidably supported by slots 36b, 37b which are engaged with pins 39 planted on a supporting member 38 slidably guided being fitted with a groove 18 and a boss 17 provided in a driven gear 19, and guide holes 36c, 37c engages with the boss 17. The driven gear 19 is rotatably supported on the shaft 11. By springs 40, 41 stretched over the driven gear 19, the engaging members 36, 37 are respectively thrusted in the rightward direction in FIG. 28, and the relative posi­tions of the projections 36a, 37a are set about half the pitch interval of the projection 13 as shown in FIG. 27, so that either one of the pair of engaging members 36, 37 may be engaged with the projection 13. FIG. 27 shows the state of engagement of the projection 36a with the projection 13. Therefore, the torque of the driving gear 12 is transmitted to the driven gear 19 by way of the engaging member 36, pin 39, supporting member 38 and groove 18. When the supporting member 38 moves in the leftward direction, the engaging members 36, 37 are also driven in the leftward direction, overcoming the thrusting force of the springs 40, 41, by the pin 39, and the engagement of the projection 36a or 37a with the projection 13 is cleared, and the torque of the driving gear 12 is not transmitted to the driven gear 19. The sup­porting member 38 has a projection 42 which abuts against the abutting member 25. The supporting plate 22 moves re­ciprocally between the non-acting position shown in FIG. 27 and the acting position shown in FIG. 29, on the chassis 10 by a known means (for example, driving of plunger by sole­noid), and is also designed to be stopped at the acting position shown in FIG. 29. Shafts 23, 24 are planted on the supporting plate 22, and they support the abutting member 25 slidaly in the lateral direction in FIG. 27 as being engaged with the guide groove 26 of the abutting member 25. Incidentally, the abutting member 25 receives a thrusting force in the leftward direction in FIG. 27 by the compres­sion spring 27 located between it and the supporting plate 22, but since the shaft 24 abuts against the edge of the guide groove 26, the abutting member 25 is stopped at the position shown in FIG. 27. Here, if the abutting member 25 is moved in the rightward direction in FIG. 27, resisting the thrusting force of the compression spring 27, the stop­ping surface 28 abuts against the shaft 23, thereby stopping at the position shown in FIG. 30. That is, the first abut­ting portion 29 and the second abutting portion 30 provided at the edge of the abutting member 25 and the projection 42 of the supporting member 38 abut against each other, and the abutting member 25 moves from the position shown in FIG. 29 up to the position shown in FIG. 30 in the rightward direc­tion, and is stopped there.

[0061] Its operation is as follows.

[0062] In FIG. 27, the supporting plate 22 is stopped at the non-acting position, in which the projection 42 of the sup­porting member 38 and the abutting member 25 are not in abutting relation. Therefore, the engaging members 36, 37 are thrusted in an obliquely right upward direction in FIG. 27 by the springs 40, 41 and the projection 36a and the projection 13 provided on the driving gear 12 are engaged with each other. For example, when the driving gear 12 is rotated and driven in the clockwise direction by a motor (not shown) in FIG. 31, the engaging member 36 having the projection 36a engages with the projection 13 is also rotat­ed and driven clockwise. Therefore, the motor torque is also transmitted to the driven gear 19, and the driven gear 19 rotates clockwise.

[0063] By contrast, the operation of not transmitting the torque of the driving gear 12 to the driven gear 19 is as follows. The supporting plate 22 is moved from the non-­acting position shown in FIG. 27 to the acting position shown in FIG. 29 by a known means (such as solenoid), and is stopped at this acting position. As a result, the first abutting portion 29 disposed at the edge of the abutting member 25 on the supporting plate 22 and the projection 42 of the supporting member 38 are ready to abut against each other. When the driving gear 12 is further rotated clock­wise from the state shown in FIG. 29, the projection 42 abuts against the first abutting portion 29. At this time, a load torque T is applied to the driven gear 19. Therefore, supposing the distance from the center of shaft 11 to the contact point of the projection 13 of driving gear 12 and the projection 36a of engaging member 36 to be R, and the tangential force at the contact point to be N, the fol­lowing relation is established.
N = T/R ----- (10)

[0064] Furthermore, supposing the coefficient of friction at the contact point to be µ, and the frictional force acting between the supporting member 38 and the groove 18 to be fʹ, the frictional force f in the sliding direction of the sup­porting member 38 on the driven gear 19 is as follows:
f = µ x N + fʹ = µ x T/R + fʹ ----- (11)

[0065] Therefore, the releasing force F to move the supporting member 38 in the direction to be isolated from the driving gear 12 in the state shown in FIG. 30 is, assuming the thrusting force in the engaging direction of the engaging members 36, 37 by the springs 40, 41 to be P, required as follows:
F = f + P ----- (12)

[0066] Here, since the thrusting force of the compression spring 27 to thrust the abutting member 25 in the leftward direction in FIG. 30 is set smaller than said releasing force F, if the projection 42 abuts against the first abut­ting portion 29, the engagement between the engaging member 36a and driving gear 12 is not disconnected, and the abut­ting member 25 is moved in the rightward direction, resist­ing the thrusting force of the compression spring 27. When the driving gear 12 further rotates clockwise, the state becomes as shown in FIG. 30, and the rightward movement of the abutting member 25 is stopped by the abutment of the shaft 23 and stopping surface 28. The driving gear 12 still continues to rotate clockwise until the projection 42 of the supporting member 38 comes to abut against the second abut­ting portion 30. At this time, since the rightward movement of the abutting member 25 is defined by the shaft 23 and stopping surface 28, and supporting member 38 moves in the leftward direction in FIG. 30 along the slope of the second abutting portion 30 of the abutting member 25, so that the engaging member 36 is moved in the leftward direction through the pin 39. Arriving at the position shown in FIG. 31, the engagement of the projections 36a, 37a of the engag­ing members 36, 37 and the projection 13 of the driving gear 12 is cleared, and the torque of the driving gear 12 is not transmitted to the driven gear 19. At this time, the frictional forces f, fʹ are eliminated, and only the thrust­ing force by the springs 40, 41 acts on the supporting mem­ber 38, but since the total thrusting force of the springs 40, 41 is set smaller than the thrusting force of the com­pression spring 27, the abutting member 25 moves the sup­porting member 38 in the leftward direction over coming the thrusting force of the springs 40, 41 as shown in FIG. 32, until the projection 13 of the driving gear 12 and the pro­jections 36a, 37a of the engaging members 36, 37 are com­pletely set apart. Therefore, if vibration or other force is applied from outside, the engaging members 36, 37 and the driving gear 12 will not be unexpectedly enchanged with each other, so that a secure disengaging operation is effected.

[0067] The above explanation refers to the engagement between the projection 13 and engaging member 36, but the same ap­plies to the engagement between the engaging member 17 and the projection 13.

[0068] Next, when the supporting plate 22 is moved from the state of not transmitting the torque shown in FIG. 32 up to the position shown in FIG. 27 by known means (such as solenoid), the supporting member 38 moves in the rightward direction in FIG. 32 by the thrusting force of the springs 40, 41 along with the movement of the abutting member 25, and either one of the projections 36a, 37a of the engaging members 36, 37 is engaged with the projection 13, so that the torque of the driving gear 12 is transmitted to the driven gear 19 by way of the supporting member 38.

[0069] At this time, the interval pitch of the projections 36a, 37a is set to be about half the pitch of the projection 13, and hence if the supporting plate 22 is moved from the position shown in FIG. 33 to the position in FIG. 27 at an arbitrary timing, at least one of the projections 36a, 37a is in a state easy to be engaged with the projection 13, so that a quick engaging action is obtained without time delay.

[0070] Or if one of the engaging members 36, 37 is broken due to some cause, a specified operation is effected by the remaining one, so that the reliability is also high.

[0071] In the above description, meanwhile, the rotation of the driving gear 12 is clockwise, but, not to mention, the same operation and effect are obtained if rotated counter­clockwise.

[0072] The projection 13 is provided inside the driving gear 12, but it is not limited to the shape shown in the drawing, and a gear may be formed or a pin may be planted, instead.

[0073] Incidentally, two engaging members 36, 37 are used in this embodiment, but three or more engaging members may be also provided.

Claims

1. A clutch assembly comprising:
a driving member;
an engaging member movable between a first position where said engaging member engages said driving member and a second position where said engaging member is apart from said driving member;
a first thrusting means for thrusting said engaging member toward said first position;
a driven member mounting thereon said engaging member and said first thrusting means and driven by said driving member through said engaging member when said engaging member is in said first position;
a releasing member movable between a position where said releasing member abuts against said engaging member and a position where said releasing member is apart from said engaging member; and
a second thrusting means for thrusting said engaging member through said releasing member toward said second position,
wherein said engaging member is moved by a driving force of said driving member to disengage from said driving member when said releasing members abuts against said engaging member, and further moved by the thrusting force of said second thrusting means through said releasing member to said second position after having disengaged from said driv­ing member whereby said driven member is released from said driving member.

2. A clutch assembly according to claim 1, wherein the thrusting force to said engaging member by said first thrusting means is smaller than the thrusting force to said releasing member by said second thrusting means.

3. A clutch assembly according to claim 1, wherein said driven member is constituted so as to rotate coaxially and integrally with said driving member through said engaging member.

4. A clutch assembly according to claim 3, wherein said engaging member is freely rotatable in the rotating direction of said driving member, while said driving member possesses a rotation defining means to define an amount of rotation of said engaging means.

5. A clutch assembly according to claim 1, wherein the releasing means comprises a defining means for defining the movement of the driven member after the driving member and engaging member are disengaged.

6. A clutch assembly comprising:
a driving member;
an engaging member movable between a first position where said engaging member engages said driving member and a second position where said engaging member is apart from said driving member;
a first thrusting means for thrusting said engaging member toward said first position;
a driven member mounting thereon said engaging member and said first thrusting means and driven by said driving member through said engaging member when said engaging member is in said first position;
a releasing member movable between a position where said releasing member abuts against said engaging member and a position where said releasing member is apart from said engaging member; and
a second thrusting means for thrusting said engaging member through said releasing member toward said second position,
wherein said driven member has an abutting portion in the vicinity of said releasing member for abutting against said releasing member when said releasing member abuts against said engaging member so that said releasing member is moved in an opposite direction to the thrusting direction of said second thrusting means, said abutting portion thereafter being released from said releasing member for allowing said engaging member to be moved to said second position by said second thrusting means through said releasing member whereby said driven member is released from said driving member.

7. A clutch assembly according to claim 6, wherein said abutting portion is abuttable against either one of both sides of said releasing member.

8. A clutch assembly according to claim 6, wherein the thrusting force to said engaging member by said first thrusting means is smaller than the thrusting force to said releasing member by said second thrusting means.

9. A clutch assembly according to claim 6, wherein said driven member is constituted so as to rotate coaxially and integrally with said driving member through said engaging member.

10. A clutch assembly comprising:
a driving member;
an engaging member movable between a first position where said engaging member engages said driving member and a second position where said engaging member is apart from said driving member;
a first thrusting means for thrusting said engaging member toward said first position;
a driven member mounting thereon said engaging member and said first thrusting means and driven by said driving member through said engaging member when said engaging member is in said first position;
a releasing member movable between a position where said releasing member abuts against said engaging member and a position where said releasing member is apart from said engaging member; and
a second thrusting means for thrusting said engaging member through said releasing toward said second position,
wherein said driven member has a first abutting portion for abutting against said releasing member so that said releasing member is moved in an opposite direction to the thrusting direction of said second thrusting means, and
wherein said releasing member has a second abutting portion for abutting against said first abutting portion so that said releasing member is moved in the opposite direc­tion to the thrusting direction of said second thrusting means, and a pushing portion which is first mved in the opposite direction to the thrusting direction of said second thrusting means by the abutment of said first and second abutting portions and thereafter pushes said engaging member in the thrusting direction of said second thrusting means to release said engaging member from said driving member whereby said driven member is released from said driving member.

11. A clutch assembly according to claim 10, wherein the thrusting force to said engaging member by said first thrusting means is smaller than the thrusting force to said releasing member by said second thrusting means.

12. A clutch assembly according to claim 10, wherein said driven member is so constituted as to be rotated co­axially and integrally with said driving member through said engaging member.

13. A clutch assembly according to claim 10, wherein said first abutting portion has a recess gradually narrowed in width toward the thrusting direction of said first thrust­ing means, while said second abutting portion has a projection gradually widened toward the thrusting direction of said second thrusting means.

14. A clutch assembly comprising:
a driving member;
an engaging member movable between a first position where said engaging member engages said driving member and a second position where said engaging member is apart from said driving member;
a first thrusting means for thrusting said engaging member toward said first position;
a driven member mounting thereon said engaging member and said first thrusting means and driven by said driving member through said engaging member when said engaging member is in said first position;
a releasing member movable between a position where said releasing member abuts against said engaging member and a position where said releasing member is apart from said engaging member; and
a second thrusting means for thrusting said engaging member through said releasing member toward said second position,
wherein said driven member has a first abutting portion for abutting against said releasing member so that said releasing member is moved in an opposite direction to the thrusting direction of said second thrusting means, and
wherein said releasing member has a second abutting portion for abutting against said first abutting portion so that said releasing member is moved in the opposite direc­tion to the thrusting direction of said second thrusting means, and a pushing portion which is first moved in the opposite direction to the thrusting direction of said second thrusting means by the abutment of said first and second abutting portions and thereafter pushes said engaging member in the thrusting direction of said second thrusting means to release said engaging member from said driving member whereby said driven member is released from said driving member, and a stopping means for stopping at a specified position the movement of said releasing member in the opposite direc­tion to the thrusting direction of said second thrusting means caused by being abutted by said engaging member, said pushing portion moving said engaging member against the thrusting force of said first thrusting means when said releasing member is stopped at said specified position thereby to disengage said engaging member from said driving member.

15. A clutch assembly according to claim 14, wherein the thrusting force to said engaging member by said first thrusting means is smaller than the thrusting force to said releasing member of said second thrusting means.

16. A clutch assembly according to claim 14, wherein said driven member is so constituted as to be rotated co­axially and integrally with said driving member through said engaging member.

17. A clutch assembly according to claim 14, wherein said first abutting portion has a recess which is gradually narrowed in width toward the thrusting direction of said first thrusting direction, while said second abutting portion has a projection gradually widened toward the thrusting direction of said second thrusting means.

18. A clutch assembly comprising:
a driving wheel;
a plurality of engaging members movable between a first position where said engaging members engage said driving wheel and a second position where said engaging members are apart from said driving wheel;
a first thrusting means for thrusting said plurality of engaging members toward said first position;
a supporting member for slidably supporting said plurality of engaging members;
a driven wheel mounting thereon said supporting member and said first thrusting means and rotated coaxially and integrally with said driving wheel through said supporting member when said engaging members are in said first position;
a releasing member movable between a position where said releasing member abuts against said supporting member and a position where said releasing member is apart from said supporting member;
a second thrusting means for thrusting said releasing member in an opposite direction to the thrusting direction of said first thrusting means; and
a stopping means for stopping at a specified position a movement of said releasing member in an opposite direction to the thrusting direction of said second thrusting means,
wherein said releasing member, when abutts against said supporting member, is moved by a rotating force of said driving wheel in the opposite direction to the thrusting force of said second thrusting means until stopped at said specified position, and thereafter said supporting member is moved by the rotating force of said driving wheel in an opposite direction to the thrusting direction of said first thrusting means until said plurality of engaging members disengaged from said driving wheel, and
wherein, after said engaging members have been disengaged from said driving wheel, said supporting member is moved by the thrusting force of said second thrusting means through said releasing member in the opposite direction to the thrust­ing direction of said first thrusting means thereby to move said engaging members to said second position whereby said driven wheel is released from said driving wheel.

19. A clutch assembly according to claim 18, wherein the thrusting force to said engaging members by said first thrusting means is smaller than the thrusting force to said releasing member by said second thrusting means.

20. A clutch assembly according to claim 18, wherein a plurality of engaging portions are provided at specified intervals on said driving wheel to be engaged with said plurality of engaging members, and engaging portions provided on said plurality of engaging members are relatively positioned accoding to said specified intervals so that at least one of them can engage at least one of said engaging portions of said driving wheel.

Drawing